Recently, a saturated polyester resin such as polyethylene terephthalate has been increasingly used as a transparent resin in place of vinyl chloride resin due to the environmental problems etc. However, since the saturated polyester resins are generally crystalline resins, and it has been difficult to crystallize them in transparent condition without using a complicated process such as orientation, those excellent characteristics including high hardness and chemical resistance which are provided by the crystallization can hardly be enjoyed according to a blow molding process wherein no orientation step is employed.